Yeah tried so hard to stay out of WWII by blockading the japanese from getting oil and by sending 100's of "liberty" ships to england. Yeah real isolationist right there mate.

lololololol it's true. In WWI there was the Lusitania too. Always thought it funny that a passenger ship would be carrying arms supplies.

But seriously, in both wars there were real, tangible threats. Iraq? Not so much. The sabre-rattling about Iran? Again, not so much... These wars are waged by the governments, with the population kicking and screaming whilst being dragged along for the ride. In WWII the US population was unified in such a way we've never seen since. It took us out of the Great Depression. Iraq and Afghanistan overwhelmingly contributed to our current recession.

edit: Iraq and Afghanistan have also seriously harmed the credibility of the United States, whereas WWI and WWII basically established our country as the leading superpower.